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What to call Occult Effects
by Kim-Ee Yeoh 12 Nov '20

12 Nov '20

By an occult effect I mean that under the type signature (M a -> M b -> M b) of a particular monad M, the two expressions (const id) and (liftM2 $ const id) are equivalent. Occult here refers to how the effect of the second parameter blocks the effect of the first one. In your opinion, is there a better word than occult to describe the property of such monads? -- -- Kim-Ee

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Re: [Haskell-cafe] What to call Occult Effects
by Kim-Ee Yeoh 12 Nov '20

12 Nov '20

On Thu, Nov 12, 2020 at 12:17 AM Justin Bailey <jgbailey(a)gmail.com> wrote: > Looking up the definition "occult" on duckduckgo > (https://duckduckgo.com/?t=ffab&q=occult+definition&ia=definition) > gives this response: > > adj. Of, relating to, or dealing with supernatural or magical > influences, agencies, or occurrences. > adj. Available only to the initiate; secret or mysterious: synonym: > mysterious. > adj. Beyond the realm of human comprehension; inscrutable. > > Doesn't seem to really apply to your type signature. If you mean in > the sense of "occlusion" or "occludes", I'd be specific ("occluded > effects"). Hi Justin, Thank you for heads up, it's just the nudge I need that "occult" probably isn't the right word although I had the astronomical usage in mind. My go-to solution is now "occlusive effects" unless something even better comes along. > > On Tue, Nov 10, 2020 at 3:24 PM Kim-Ee Yeoh <ky3(a)atamo.com> wrote: > > > > By an occult effect I mean that under the type signature (M a -> M b -> > M b) of a particular monad M, the two expressions (const id) and (liftM2 $ > const id) are equivalent. > > > > Occult here refers to how the effect of the second parameter blocks the > effect of the first one. > > > > In your opinion, is there a better word than occult to describe the > property of such monads? > > -- > > -- Kim-Ee > > _______________________________________________ > > Haskell-Cafe mailing list > > To (un)subscribe, modify options or view archives go to: > > http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe > > Only members subscribed via the mailman list are allowed to post. > -- -- Kim-Ee

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Re: [Haskell-cafe] What to call Occult Effects (Kim-Ee Yeoh)
by Olaf Klinke 12 Nov '20

12 Nov '20

> By an occult effect I mean that under the type signature (M a -> M b > -> M > b) of a particular monad M, the two expressions (const id) and > (liftM2 $ > const id) are equivalent. > > Occult here refers to how the effect of the second parameter blocks > the > effect of the first one. > > In your opinion, is there a better word than occult to describe the > property of such monads? Dear Kim-Ee, TL;DR: Why not the simpler do {y <- b; a} = a My name for your property would be "distribution-like" or "lazy" because of an old post of mine [1]. In that thread we discussed models of probability and I emphasized the property fmap.const = const.return :: a -> M b -> M a (Functor-const) which we will see is equivalent to your occultness. Categorically it can be re-phrased as: "M as a functor maps constant functions to constant functions." First, instead of `const id` I will use `const`, that is, we shall prove const = liftM2 const :: M a -> M b -> M a (occultness) which I believe should be equivalent to your property. For the proof it will be convenient to use the following. Lemma: liftM2 f a b = a >>= (\x -> fmap (f x) b) Proof: We de-sugar the do-notation in the source code for liftM2. liftM2 f a b = a >>= (\x -> b >>= (\y -> return (f x y))) Now use the equation fmap h b = b >>= (\y -> return (h y)) with h instantiated to `f x` to obtain the desired identity. q.e.d. Armed with the Lemma we instantiate f = const. liftM2 const a b = a >>= (\x -> fmap (const x) b) If we now assume my property (Functor-const) then we may re-write to liftM2 const a b = a >>= (\x -> const (return x) b) = a >>= (\x -> return x) = a We have shown (Functor-const) implies (occultness). For the reverse implication, we shall prove (Functor-const) holds with the arguments swapped, that is, we prove the equation \b -> \x -> fmap (const x) b = \b -> \x -> return x Starting with the left-hand side, we eta-expand using the law (k :: a -> M b) x = return x >>= k and obtain \b -> \x -> (return x >>= (\x -> fmap (const x) b)) Using the Lemma we identify the expression in the outermost parentheses as liftM2 const (return x) b which by assumption equals return x, whence we re-write the entire term to \b -> \x -> return x q.e.d. Next consider a law with the same type as (occultness): (=<<).const = const :: M a -> M b -> M a (Kleisli-const) do {y <- b; a} = a (same in do-notation) Any MonadPlus fails this due to the law k =<< mzero = mzero. Categorically it can be re-phrased as "The functor from the Kleisli category of M to Hask preserves constant arrows." I will prove that if M is commutative then (Kleisli-const) implies (occultness). liftM2 const a b = do {x <- a; y <- b; return (const x y)} = do {y <- b; x <- a; return (const x y)} (by commutative) = do {y <- b; x <- a; return x} = do {y <- b; a} = a (by Kleisli-const) Probability distributions have property (Functor-const) because it essentially says that if you map any distribution through a constant function, you will end up with all mass in one place. It is related to lazyness because a priori const a :: M b -> M a is lazy in its argument whereas \b -> a >>= (\x -> fmap (const x) b) is not lazy a priori, i.e. may examine its argument b and execute side- effects. Such lazyness was desired in [1] because inspecting an argument in that context meant computationally expensive sampling of a random distribution. Are there concrete Haskell monads with this property? NonEmpty lists have this property up to multiplicity and order, that is, non-empty finite sets are an example of an occult M. The Reader monad is easily seen to have this property. And that seems to be all. Observe that my two example monads above are indeed commutative and have the property (Kleisli-const). I'm curious whether (Kleisli-const) makes sense in your application. Olaf [1] https://mail.haskell.org/pipermail/haskell-cafe/2019-October/131605.html

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Three new Teaching Assistant positions in Nottingham
by Graham Hutton 11 Nov '20

11 Nov '20

Dear all, As part of a strategic expansion, the School of Computer Science at the University of Nottingham is seeking to make three new permanent appointments at Teaching Assistant level: https://www.nottingham.ac.uk/jobs/currentvacancies/ref/SCI290020 Applicants with expertise in functional programming are strongly encouraged! The deadline for applications is 11th December 2020. Best wishes, Graham — Professor Graham Hutton School of Computer Science University of Nottingham, UK http://www.cs.nott.ac.uk/~pszgmh This message and any attachment are intended solely for the addressee and may contain confidential information. If you have received this message in error, please contact the sender and delete the email and attachment. Any views or opinions expressed by the author of this email do not necessarily reflect the views of the University of Nottingham. Email communications with the University of Nottingham may be monitored where permitted by law.

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Re: [Haskell-cafe] Occult effects...
by Michal J Gajda 11 Nov '20

11 Nov '20

It is easier to understand it if: 1. You give some examples of such monads 2. Describe how this property arises 3. Tell how whether the law is unique or part of a list of laws applicable Most of mathematics we do is not entirely disconnected from applications. If I tell you there is a class of monoids `m` over a set of objects `o` : class Monoid m => T m o where i :: o -> t c :: t -> o -> Bool Such that the following laws are satisfied: Forall x y z m n. c (i x) x =True c mempty x = False c m y = True => c (m <> n) y = True c n y = True => c (m <> n) y = True What does it tell you about the definitions? Can you tell if this set of laws is correctly stated or exhaustive? Whether it models what I intend to do? Without further examples could I claim that it may be universal model for some phenomena f and g? Or would you rather see some examples or descriptions of i and c operations? PS you may respond to haskell-cafe, sure. I did not think that my previous question deserved sharing, but this answer certainly does. -- Cheers Michał On Wed, Nov 11, 2020, 14:04 Kim-Ee Yeoh <ky3(a)atamo.com> wrote: > Hi Michal, > > How is it hermetic? I think I fully described the property whose name I am > opening to discussion. > > What is lacking in the definition? > > Also, do you mind having this discussion at the cafe itself? You are > probably not the only one with this query. > > On Wed, Nov 11, 2020 at 7:37 PM Michał J Gajda <mjgajda(a)gmail.com> wrote: > >> Hi, >> Your post to haskell-cafe is somewhat hermetic if you do not provide >> additional examples. >> What do you use these for? >> -- >> Cheers >> Michał >> > -- > -- Kim-Ee >

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Last Call for Contributions: BOB 2021 [Feb 26, Deadline Nov 13]
by Stefan Wehr 10 Nov '20

10 Nov '20

BOB Conference 2021 "What happens when we use what's best for a change?" http://bobkonf.de/2021/cfc.html Berlin, February 26 Call for Contributions Deadline: November 13, 2020 You are actively engaged in advanced software engineering methods, implement ambitious architectures and are open to cutting-edge innovation? Attend this conference, meet people that share your goals, and get to know the best software tools and technologies available today. We strive to offer a day full of new experiences and impressions that you can use to immediately improve your daily life as a software developer. If you share our vision and want to contribute, submit a proposal for a talk or tutorial! NOTE: The conference fee will be waived for presenters. Travel expenses will not be covered (for exceptions see "Speaker Grants"). Online or Onsite We do know yet whether BOB will happen onsite in Berlin or as an online event. Should BOB happen online, we will likely ask for pre-recorded talks to make room for questions and social interactions during the actual conference day. (Of course, we'll provide assistance making those recordings.) Tutorials will likely happen as a live-session. Speaker Grants -------------- BOB has Speaker Grants available to support speakers from groups under-represented in technology. We specifically seek women speakers, speakers of color, and speakers who are not be able to attend the conference for financial reasons. Shepherding ----------- The program committee offers shepherding to all speakers. Shepherding provides speakers assistance with preparing their sessions. Specifically: - advice on structure and presentation - review of talk slides - assistance with recording - review of recording, if applicable Topics ------ We are looking for talks about best-of-breed software technology, e.g.: - functional programming - persistent data structures and databases - event-based modelling and architecture - types - formal methods for correctness and robustness - abstractions for concurrency and parallelism - metaprogramming - probabilistic programming - math and programming - controlled side effects - beyond REST and SOAP - effective abstractions for data analytics - … everything really that isn’t mainstream, but you think should be. Presenters should provide the audience with information that is practically useful for software developers. We're especially interested in experience reports. Other topics are also relevant, e.g.: - introductory talks on technical background - overviews of a given field - demos and how-tos Requirements ------------ We accept proposals for presentations of 45 minutes (40 minutes talk + 5 minutes questions), as well as 90 minute tutorials for beginners. The language of presentation should be either English or German. Your proposal should include (in your presentation language of choice): - An abstract of max. 1500 characters. - A short bio/cv - Contact information (including at least email address) - A list of 3-5 concrete ideas of how your work can be applied in a developer's daily life - additional material (websites, blogs, slides, videos of past presentations, …) - Don't be confused: The system calls a submission event. Organisation ------------ - Direct questions to contact at bobkonf dot de - Proposal deadline: November 13, 2020 - Notification: November 27, 2020 - Program: December 6, 2020 Submit here: https://bobcfc.active-group.de/en/bob2021/cfp Program Committee ----------------- (more information here: https://bobkonf.de/2020/programmkomitee.html) - Matthias Fischmann, Wire - Matthias Neubauer, SICK AG - Nicole Rauch, Softwareentwicklung und Entwicklungscoaching - Michael Sperber, Active Group - Stefan Wehr, Hochschule Offenburg Scientific Advisory Board - Annette Bieniusa, TU Kaiserslautern - Torsten Grust, Uni Tübingen - Peter Thiemann, Uni Freiburg

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Extended Deadline - Compiler Construction (CC) 2021
by Delphine Demange 09 Nov '20

09 Nov '20

ACM SIGPLAN 2021 International Conference on Compiler Construction (CC 2021) Co-located with CGO, HPCA and PPoPP Tue 2 - Wed 3 March 2021 https://conf.researchr.org/home/CC-2021 CALL FOR PAPERS The International Conference on Compiler Construction (CC) is interested in work on processing programs in the most general sense: analyzing, transforming or executing input that describes how a system operates, including traditional compiler construction as a special case. The abstract and full paper submission is now November 13, 2020. = IMPORTANT DATES = Abstract & Full Paper Submission: November 13, 2020 (EXTENDED) Author Response Period: December 7 - 9, 2020 Author Notification: December 22, 2020 Artifact Submission: January 5, 2021 AE Notification: January 20, 2021 Final Papers due: January 22, 2021 Conference: March 2 - 3, 2021 Original contributions are solicited on the topics of interest which include, but are not limited to: - Compilation and interpretation techniques, including program representation, analysis, and transformation; code generation, optimization, and synthesis; the verification thereof - Run-time techniques, including memory management, virtual machines, and dynamic and just-in-time compilation - Programming tools, including refactoring editors, checkers, verifiers, compilers, debuggers, and profilers - Techniques, ranging from programming languages to micro-architectural support, for specific domains such as secure, parallel, distributed, embedded or mobile environments - Design and implementation of novel language constructs, programming models, and domain-specific languages CC is an ACM SIGPLAN conference, and implements guidelines and procedures recommended by SIGPLAN (https://www.sigplan.org) Prospective authors should be aware of SIGPLAN’s Copyright policies. Proceedings will be made available online in the ACM digital library from one week before to one week after the conference. Full CfP: https://conf.researchr.org/track/CC-2021/cc-research-papers ARTIFACT EVALUATION Authors of accepted papers will be invited to submit their artifacts for the Artifact Evaluation (AE). The Artifact Evaluation process begins after the acceptance notification, and is run by a separate committee whose task is to assess how the artifacts support the work described in the papers. To ease the organization of the AE committee, we kindly ask authors to indicate at the time they submit the paper, whether they are interested in submitting an artifact. Papers that go through the Artifact Evaluation process successfully will receive a seal of approval printed on the papers themselves. Authors of accepted papers are encouraged, but not required, to make these materials publicly available upon publication of the proceedings, by including them as “source materials” in the ACM Digital Library. CC AE web page: https://conf.researchr.org/track/CC-2021/research-artifacts ORGANIZERS General Chair: Aaron Smith - Microsoft / University of Edinburgh Program Chairs: Delphine Demange - Univ Rennes, Inria, CNRS, IRISA Rajiv Gupta - UC Riverside Artifact Evaluation Chairs: Bruno Bodin - Yale-NUS College Michel Steuwer - University of Glasgow Web Chair: Martin Lücke - University of Edinburgh Steering Committee: Björn Franke (Chair) - University of Edinburgh Jose Nelson Amaral - University of Alberta Christophe Dubach - University of Edinburgh Sebastian Hack - Saarland University Manuel Hermenegildo - IMDEA Software Institute and T.U. of Madrid (UPM) Alexandra Jimborean - University of Murcia Milind Kulkarni - Purdue University Louis-Noël Pouchet - Colorado State University Peng Wu - Futurewei Technologies Jingling Xue - UNSW Sydney Ayal Zaks - Intel Corporation and Technion Program Committee: Guillaume Baudart - IBM Research Walter Binder - University of Lugano Simone Campanoni - Northwestern University Albert Cohen - Google Caroline Collange - Inria, Univ Rennes, CNRS, IRISA Huimin Cui - Institute of Computing Technology, CAS Christophe Dubach - McGill University Benoît Dupont de Dinechin - Kalray Bernhard Egger - Seoul National University Christine Flood - Red Hat Laure Gonnord - University of Lyon and LIP Myoungsoo Jung - KAIST Andrew Kennedy - Facebook Dongyoon Lee - Stony Brook University Christian Lengauer - University of Passau Xavier Leroy - Collège de France and Inria Yun Liang - Peking University Toby Murray - University of Melbourne and Data61 Biswabandan Panda - Indian Institute of Technology Kanpur Santosh Pande - Georgia Tech Louis-Noël Pouchet - Colorado State University Gabriel Rodríguez - Universidade da Coruña Jan Vitek - Northeastern University Jingling Xue - UNSW Sydney Zhijia Zhao - UC Riverside

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Call for Workshop Proposals: ICFP 2021
by Sam Tobin-Hochstadt 05 Nov '20

05 Nov '20

CALL FOR WORKSHOP AND CO-LOCATED EVENT PROPOSALS ICFP 2021 26th ACM SIGPLAN International Conference on Functional Programming August 22 - 27, 2021 Daejon, Korea https://icfp21.sigplan.org/ The 26th ACM SIGPLAN International Conference on Functional Programming will be held in Daejon, Korea on August 22-27, 2021, with the possibility of a virtual conference. ICFP provides a forum for researchers and developers to hear about the latest work on the design, implementations, principles, and uses of functional programming. Proposals are invited for workshops (and other co-located events, such as symposiums) to be affiliated with ICFP 2021 and sponsored by SIGPLAN. These events should be less formal and more focused than ICFP itself, include sessions that enable interaction among the attendees, and foster the exchange of new ideas. The preference is for one-day events, but other schedules can also be considered. The workshops are scheduled to occur on August 22rd (the day before ICFP) and 26-27th of August (the two days after ICFP). ---------------------------------------------------------------------- Submission details Deadline for submission: November 27, 2020 Notification of acceptance: December 15, 2020 Prospective organizers of workshops or other co-located events are invited to submit a completed workshop proposal form in plain text format to the ICFP 2021 workshop co-chairs (Leonidas Lampropoulos and Zoe Paraskevopoulou) via email to icfp-workshops-2021(a)googlegroups.com by November 27, 2020. (For proposals of co-located events other than workshops, please fill in the workshop proposal form and just leave blank any sections that do not apply.) Please note that this is a firm deadline. Organizers will be notified if their event proposal is accepted by December 15, 2020, and if successful, depending on the event, they will be asked to produce a final report after the event has taken place that is suitable for publication in SIGPLAN Notices. The proposal form is available at: http://www.icfpconference.org/icfp2021-files/icfp21-workshops-form.txt Further information about SIGPLAN sponsorship is available at: http://www.sigplan.org/Resources/Proposals/Sponsored/ ---------------------------------------------------------------------- Selection committee The proposals will be evaluated by a committee comprising the following members of the ICFP 2021 organizing committee, together with the members of the SIGPLAN executive committee. Workshop Co-Chair: Zoe Paraskevopoulou (Northeastern University) Workshop Co-Chair: Leonidas Lampropoulos (University of Maryland) General Chair: Sukyoung Ryu (KAIST) Program Chair: Ronald Garcia (University of British Columbia) ---------------------------------------------------------------------- Further information Any queries should be addressed to the workshop co-chairs (Zoe Paraskevopoulou and Leonidas Lampropoulos), via email to icfp-workshops-2021(a)googlegroups.com.

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Announcing the Haskell Foundation
by Richard Eisenberg 04 Nov '20

04 Nov '20

I'm very pleased to announce the creation of the Haskell Foundation (HF), an independent, non-profit organisation dedicated to broadening Haskell adoption. Website: https://haskell.foundation/ <https://haskell.foundation/> Twitter: @haskellfound Founding whitepaper: https://haskell.foundation/whitepaper/ <https://haskell.foundation/whitepaper/> Simon Peyton Jones's announcement, with lots of Q&A: https://www.youtube.com/watch?v=MEmRarBL9kw <https://www.youtube.com/watch?v=MEmRarBL9kw> The "official" ask-me-anything on Reddit: https://www.reddit.com/r/haskell/comments/jnwg7i/haskell_foundation_ama/ <https://www.reddit.com/r/haskell/comments/jnwg7i/haskell_foundation_ama/> Mailing list for future HF announcements: https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-announce <https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-announce> Mailing list for HF discussion / involvement: https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-discuss <https://mail.haskell.org/cgi-bin/mailman/listinfo/hf-discuss> Please join the conversation. We need your participation to realize the vision of the foundation as *our* foundation, not *their* foundation. Looking forward to seeing where this all leads! Richard

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Re: [Haskell-cafe] Looking for maintainers or comaintainers on my Haskell projects
by Michal J Gajda 04 Nov '20

04 Nov '20

Hi Chris., > If you want to take xeno and make it into a publishable package, please do so. We have offered to take over xeno over a year ago, and this offer still stands backed by me personally. Since I have made a few contributions, you may know that I would deliver here. To add me as maintainer on Hackage: MichalGajda To add me on GitHub: mgajda -- Cheers Michał

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